Questions | Mimamsa 2021

Bio Brief Thought 1


The setup for this experiment is quite straightforward. The neural circuit - consisting of a single pair of neurons and some downstream neurons - is isolated from the organism and placed in the centre of an elliptical path.

As shown in the diagram above, a pair of mechanosensitive neurons - shown in green - are opposite each other with five downstream neurons in between them that would carry forward their signal - these are shown in red. Both the neurons have excitatory connections to the five downstream neurons - from A to E. Researchers are already aware that stimulating these neurons mechanically (using vibrations, for example) will increase their firing rate. A seismic wave generator is placed some distance away from this apparatus, equidistant from both mechanosensitive neurons. This would periodically release bursts of waves through the ground towards the receptors, as seen by the dotted lines in the diagram.

A trial consists of firing a short-lived burst of waves towards the neural circuit and observing the almost instantaneous responses of the central neurons. Then, the generator is shifted a little further down the elliptical path and another trial is conducted. Multiple similar trials are conducted until a full orbit along the path is completed and the generator returns to its original position. The time needed for the propagation of waves from the generator to the neurons is chosen in such a way that it is comparable to the time taken for one single action potential.

The researchers are trying to answer two main questions - how the rate of the action potentials of the neurons changes as the generator makes its clockwise orbit around them and what its function was. Can you deduce what researchers found through their experiments?

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